1993 Ford Thunderbird high idle problem

[quote:c30298ea7c="eddiekempker"]Engine Performance problem
1993 Ford Thunderbird 6 cyl Two Wheel Drive Automatic 150000 miles

I have a 2500 rpm sustained idle. The idle set screw is not adjusted too far. I changed the air flow sensor next to the air filter - not the problem. I changed the idle air control valve with a new part - same problem. The Throttle body butterfly valve does not seem to have any impaired movement (buildup blocking open & close function). What else could it be? Interesting note: prior to changing the iac valve, I had one from a 96 mustang 6 cyl that I put on after modifying the wire connector, and the idle was normal, but little to no power. also when proper iac is installed, and you unhook the air hose to expose the throttle body butterfly valve the idle goes way down and you have to adjust the idle set screw much further down to even out idle. Any other thoughts?[/quote:c30298ea7c]

It sounds like the idle air control valve. A couple of questions, is the gasket leaking at al? Also look close to be sure the housing isn't slightly cracked. I had the same problem earlier this year and it was the iac.